A corpora



'.Ju'n 2l, 1932. L, L.. CUNNINGHAM Re 18,503

REGULATING SYSTEM original Fi'led'July 23V. 1924 x n INvaN-ron )1i Law; l... C NNINGHAM 9/ l? /v l" ATTORNEYS Reiuuecl June v.21, 1932 i UNITED STATES PATENT: OFFICE LEWIS L. CUNNINGHA, OIF-MINNEAPOLIS, MINNESOTA, ASSIGNOR TO MINNEAPOLIS-I HONEYWELL REGULATOR COMPANY, F vMZIZNNEAPOLIS, MINNESOTA, A CORPORA- TION 0F DELAWARE aneum'rmc SYSTEM rlglual application led Iuly a3, 1924, Serial No. 727,836. Renewed November 16, 1929. Original No. 1,768,890, dated July 1, 1930.l Application for reissue led May 16, 1931. Serial No. 537,966.

This invention relates to improvements in apparatus adapted to automatically regulate physical conditions at the point of control, t o substantially prevent variation in such conditions, or to permit such; variation only in some predetermined degreey which is determined by the adjustment ofthe apparatus.

The invention finds valuable application in the control of furnace or other temperatures, and Where it is desirablev to yhave the temperature under control vary as little as is practicable, between predetermined limits. The invention also finds valuable application for controlling sources of fuel supply such as gas, oil or electricity, and byits use,

the supply of fuel to a burner may be controlled by any suitable mechanism which can be actuated by a suitable electrically controllable means such as a motor, for example a reversible motor.

The method of this invention is adeparture from the commonly used two point control. In the latter method, any suitable thermometer havin a movable member is utilized to close an' open an. electric circuit through asolenoid, which operatesv a valve or other mechanism, to control fuel input The pur `e of the vsystem herein is to` automatical supply heat at a steady rate, and to so adjust the supply as to maintain an even temperature between the permissible upper and lower operating limits, and very close to the desired operating point. The

invention is adapted for a large rangefof applications for regulation of various kinds of Y physical effects. n y' 5 It is one of the objects of this invention to provide a control system wherein the variationl of the condition to be controlled can be delicately measured or regulated` and wherein small changes in .the condition are caused to produce mechanical movements of suicient magnitude to operate a switch or equivalentdevice in such manner that the full operating cyclev is not immediately accomplished or does not pass immediately from limit to limit, but is accomplished in part, gradually or in smallincreme'nts, in substantially exact Vaccordance with the changing conditions at point of control, and then continues in the same direction in correspondence to the similar change "'of condition, or the control may act intermittently and/or reversely in some predetermined relation.

In the drawing a special type of thern1o1n eter has been illustrated, but there is no inments of the invention. to the furnace under control. When the tem- Referring to the drawing: Numeral 1 indicates a thermo-couple shown associated with a heat producing device, such as a burner, the fuel supply for which burner is to be controlled. kThese elements are symbolic of' a physical condition to be controlled, and of means for varying the physical condition. This heat supply element or condition-changer is indicated at 2. A supply pipe for the burner is indicated at 3, and a valve for controllingV the pipe is indicated at 4. The thermo-'couple r1 is assumed to be located at the pointwhere temperature is to be controlled land is connected to r4a potentiometer system, parts of which are respectively indicated at 6 7. The drum 8 is adapted to move with resistance 6 of the potentiometer. ing apparatus (not shown) operates to rotate the drumuntil the electro-motive force developed by the thermcouple 1 is balanced yl the potential drop in resistance 6 vbetween the points towhich the thermo-coun automatic self-balanc- 'but merely illustrates one type of thermometer with which the invention can be used.

' In this description, as in actual practice,

movement of the member 11 to the left corresponds to a lowering of the temperature under control, and the movement to the right, to a rise of thattemperature.

Numeral 15 indicates a gear or any other suitable element capable of any kind ofY motion) connecte by any suitable PNmeans such as shaft l18 with valve 4, so that when the gear is rotated in one direction, the valve moves in closing direction, and when the gear moves in an opposite direction, the valve correspondingly moves in opening direction. Any form of controller may be substituted for the valve, provided that the movement of such controller correspondingly varies the rate of heatdelivery to the thermocouple. It is conceivable-that the element 1 5 or its e uivalent may be attached to the rotor of a vo tage regulator or to a valve controlling as or air or other medium, and ythat it may efmechanically connected to another 'valve so that' gas and' air may be controlled simultaneously or it may be connected to a mixing valve. It is clear that the actual for rotating the element 15 con worm gearing is shown. Any type of motor Y. motor for reversing means of control of-heat or other supply may be varied to suit the variousconditions and in accordance with the character of the source of heat energy. Rotation of the gear 15 in one direction ma result in vdecrease in rate of heat energy elivery tothe furnaceand a rotation inthe opposite direction may result in. an increased rate of delivery:

A reversible motor 16 is suitabl connected fbrmably to direction of rotation of the motor rotor;

may be used, although the reversible type is clalmed in combination. In circuit with the it, is a selectively operable rela generally indicated at 17.

Slidab i Carried by the b1o1ck, but suitably insulated therefrom, and from one another,

i of bars respectively indicated22-23. These bars are spacedapart asf at 24, in this inand suitably stance slightly spaced. T liebar 22 is connected b conductor 25 with a brush 26 con tacting 't switch segment 28 carried 'by insulated` :from the rotatable member 15. Brush 29 contacts the same segment 28 and conductor 30 connects-this brush with one end of coil ofthe relay. `The y mounted on a bar 20 is a block 21.v

are a pair.

tor 38 to brush 42 contacting with limit switch segment 43 of member 15. Brush 44 contacts the .same segment and is connected by conductor 45 with one end of magnet coil 46. The other -end of this coil is connected by conductor 47 with conductor 33 and, therefore, with line 34. Armature 40 is adapted to be alternatively attracted according as coil 31 or 46 is energized. Arm 40 operates the A contacts for reversing the motor in the usual manner. r v

Motion of block 2 1, and, therefore, of the contacts 22, 23, is controlled by element 15, in this instance, mechanically, and means is provided whereby the ratio of degree of motion between 21 and 15 `can be varied. It is conceivable, however, that the motion control could be electrical, and there is no intention to limit the invention to the particular means shown. Suitably fastened tol the gear 15 is a member 50 having arms diametrically related to the pivotal axis 49 of the gear, and to this member, at 4one side .of its. pivot, is secured as at 51, the end of a wire or .other flexible element 52 having one portion suitably guided as at 53, and adjustably connected to the slide 21, as at 54. The otherportion of the wire is guided by suitable means 156,"and the opposite end is .connected as 'at l57 to the member 50 at the opposite side'of -the axis 49. This wire may pass through' suitable housing 58 and a Weight 59 acts as slack take-u the e ective length o cable 52. This will also compensate for temperature changes. By loosening screw 54, the block 21 may be moved independently re-clamped to the wlre at any suitable position. Rotation of the gear 15 results inmotionof the member 21, and i is evident that the movement ofthe element 2 may be made any desired function of the degree of gear rotation by suitably altering the size or shape of the member 50, or by securing the ends of the wire at pointsk nearer to or farther from the axis 49.

lOperation lIf the indicator 1l moves sufficiently, as it .will on suficient change of temperature at the thermo-couple 1, contact 37 will engage either bar 22 or'bar 23, depending on the directiony of 'motionand on thedirection of.

of the wire, and thenl` ica 1054 means, to provide for alteration in f temperature change at the thermo-couple. Let it be assumed that the temperature moves downwardly, then the ti of element 37 makes v electrical contact with ar 22, and a circuit is closed through coil 31 of the relay as follows: 35, 36, 37, 22, 25, 26, switch segment 28, 29, 30, 31, 32, 33 to 34. The armature 40 of 'the relay 17 will, in this instance, be moved to the left and the motor circuit closed by means of one of the switching elements controlled by the armature. The motor will then rotate in a predetermined direction 'so as to correspondingly increase the rate of lheat delivery to the point under temperature control Conversely when the contact 37 moves in the opposite direction and engages the bar 23, coil 46 is energized, and the motor reversed, and the element 15 rotated in an opposite direction to decrease the rate-ofuheat delivery. In the latter instance, the circuit is as follows: 35, 36, 37, 23, 38, 42, 43, 44, 45,

coil 46, conductor 47, conductor 33, to line 34.A

The armature 40 will then be movedto the right and the motor will be. reversed by the other armature-controlled 'switching element. n

Motor 16 will continue to operate as long as 37 and 22 remain in contact, but a slight motion of slide 21, and therefore of the bar 22 to the left will break the contact, and when this occurs, the motor will stop. The result, therefore, is an adjustment of the rate of delivery of heat energy at-the point 1, under temperature control, and it is clear that by properly controlling the sliding motion y(or any other suitable motion)v of element 21, any desired control of temperature may be ef- It is seen that the electrical and mechanical connections can be so adjusted that when contact is made, for example between the bar 22 and the ymember 37, the slide 21 will be moved to the left until contact is. broken, at which time the motor will stop, due to deenergization of relay coil 31 and movement of the switch to the position shown in the drawing. If the temperature at the thermocouple continues to fall, the contact 37 will be againnioved to the left and contact will again be made with bar 22 and rotation of the gear will continue in the same direction, and consequently .the ratelof delivery 'of heat energy at the thermo-couple by the element 2 will be increased. This operation may be repeated until the heat balanceis obtained, or

Y unt-il the element 18 operated by the gear 15 has reached its maximum supply position. Obviously, after thsJinaximum supply position is reached, it is not desirable to permit .a continued 'rotation of the gear 15 -in that direction. The limit switch 28 prevents this V- lower temperature.

continued rotation, by opening* the circuit through the bar 22 and coil 31, and thus the system becomes inoperative inl regard to any If the temperature at the thermo-couple 1 rises, and member 37 moves a sufficient distance to the right, then the circuit through the coil 46 is closed, and the armature 40 moves to the right to reverse the direction of rotation of the motor and of element l5, and the slide 21 moves to the right to break contact between bar 23 and contact 37. This operation will then be repeated in the same direction until the heat balance in the opposite direction is obtained, or until the element 18 has reached vits minimum supply position, at which time the limit switch 43 acts to break the electric circuit through bar 23 and coil 46. It is to be noted thatthe coil 3l of the relay 37 is again energized as soon as the sliding member 21 has moved appreciabl-y to the right.

`Usually, in practice, the furnace tempera tureis required to be maintained between definite upper and lower limits, For example, normal temperature may be one thousand degrees with a permissible variation of twenty-five degrees plus or minus, giving a range of fifty degrees. In this case,the

corresponding to fifty degrees on the scale 13.`

It is clear that when the indicator 37 has moved to the ninehundred seventy-five de- Y gree mark on the scale, the heat supply mechanism will be in a position corresponding to the maximum rate of delivery of heat energy, and when the indicator arrives at the ten hundred twenty-five degree mark, the heat supply mechanism will beat a position corresponding to the minimum rate ofheat delivery. The apparatus, therefore, always tends to adjust itself so as to produce a stable operating temperature between the operating limits for which it is adjusted. In many cases, it is found'desirable to accelerate-l the rate of heat in-put to the furnace, with an increasing departure from the normal temperature. With thissystem, this may be easily accomplished by substituting a differently shaped member 50, or bychanging the points of connection ,ofr the ends of the wire 52 relative to the axis 49. For example, as lshown in the dra a certain degree of motion of the gear, 15 will cause the indicator'orlcontact?, to move acertainf distance along thescale. 4During rotation of the gear 15from the position shown, and until the member 50 is perpendicular to its original position, the @degree of motion of the slide 21 is lproportionately lessened. The' member f5() and the mechanical connectionsl any desired function of thedeparture of the temperature at the thermo-couple 1, from the normal temperature, by altering the position of the connections relative to the axis 49.

Provision is made for changes which may be required, in point of temperature control, by having the cable 52 adjustably fastened -to the slide 21 by meansof the screw or equivalenut element 54. For example, if the gear 15 beplaced in a positionv corresponding tokcable 52at that position on'the scale which corresponds tothe desired point of temperature control, then the system will be operated in such a Way as to tend to bring the temperature at the point of control to the desired value. y

Under normal conditions, the bars 22 and 23 do not have to be very long, because the end ofthe element 37 is always between the ends of the bars. By having the bars of a greater length,` however, contactV with either ar is maintained and the system will allWays tend to operate to a balance, even though initially the position of the element 7 is far removed from the space between the ars.

In manycases where the temperature of the\furnace under control is subject to sudden and comparatively large variations, due to loading or other conditions, it is desirable'as far as possible to have the control system anticipate these changes. Tomeet these conditions, the contact point 37 has the form `of a lever pivoted as at to the element 11.

Springs 66 are arranged at opposite sides o the upper portion of the lever 37 and are held by adjusting screws 67 carried. by the indicator or'slide 11, and these springs tend to maintain the axis of the element 37 perpendicular to the direction of motion of the slide 11 to the long dimension of the scale and to direction of motion of the block 21.

F astened to the lever 37 is the endless cable 69 which passes around a suitable pulley 70 and around a second pulley 71 which latter pulley is arranged von the Yspindle of a rotary dashpot 72. The dash-pot is so arranged that by altering the height of the container 73 the retarding effect may be altered.

It is clear that a sudden motion of the in'- dicator 37 `due to a sudden change of tem'- perature at the point of controlwill result in disturbing the right-angularrelation of the indicator 37' with respect to the direction of motion of the slide 11. In such a case, the

ear 15 would be rotated farther than would ge the case if the dash-pot were used,-and the rate of heat in-put to the furnace would, therefore, be accelerated more than would otherwise'be the case. By adjusting the dash- `pot to obtain the proper retarding effect, the rate of heat'in-put to the furnace may be made any desired function of'the rate of change of the .temperature under control.

It is to be .noted that this -dash-pot -action is superposed 'upon or is complementary to -the i previously described action, due to the actual departure of the temperature from the normal value.

l,Under certain conditions, it maybe desirable `to-have the motor 16 rotate appreciablyafter the contact between 37 and 22 or' 23 is broken, so that adjustments of the rate of heat in-put will be fewer but of larger value. the motor may be equippedI with a flywheel of any desired moment of inertia so that after the current is cut off from the motor, it will continue to rotatel appreciably. This will re' sult in control steps which are somewhat larger but less frequent. Conversely, an automatic solenoid operated brake may be used which will release While the voltage is applied to the motor but will rip instantly when current is'interrupted. perating conditions will 'determine which of these methods 'shall beused, although-in many cases neither will be used, since the moment of inertia of the armature will be sufficient to supply the necessary over-run.

It is clear that the operation of'this systemr is Vnot necessarily confined to use with an indicator having a straight line horizontal motion such as illustrated. vMany indicators have a circular path or motion and it is .obvious that the system may be adapted to this circular motion without altering the essential elements of this invention. I, therefore, reserve the right to iall such modifica- In this case, the armature shaft of tions as may fall Within the spirit of the appended claims. ,fl Y

I claim as my invention:

1. In a temperature control system the combination of a temperature indicating member automatically movable in response y a'reversible electrical ido mitting motion ofthe said rotative energy control member to the said pair of electrical contacts; and a cam 'shaped member ada ted to cooperate with the said flexible ca 1e means and to predetermine for different angular positions ofthe said rotative enerf' y control member, the ratio of motion of t e said pair of movable contacts with respect to motion of the said rotative energy control member.

2. A temperature control system including an electrical contactcarried by a temperature indicating member; a pair of movable electrical contacts, fixedl with respect to each other and cooperating with the said electrical contact, for the reversible control of an electrical motor; a. heat delivery control member actuated by the said electrical motor; a cam shapedy member in mechanical relation with the said heat control member; afiexible cable, adaptedly means of pulleys, to transmit motion of the said cam shaped member to the said f' pair of electrical contactsso that motion of the said pair of electrical contacts may be inl any desired function of motion of the said heat control member, and the resultant control of the rate of heat delivery to th'e point under temperature control maybe in any desired function of the temperature at the point under` temperature control.

3. A temperature control syste-m including a pair of electrical contacts adapted to cooperate with an electrical contact, movable in response to change of temperature at the point under temperature control, for the control of an electrical motor, said motor being adapted to actuate a heat delivery control member; mechanical means of transmitting, in any desired ratio, motion of the saidv heat deliver control member to a flexible cable, said cable being adapted to move the said pair of electrical contacts, and mechanical means adapted to movably fix the position of the said pair of electrical contacts relative to a fixed point on the said flexible cable so that the normal point of temperature control may thereby be changed. l

4. A temperature control system having a temperature indicator; an electrical contactor carried by the said temperature indicator; a pair of contacts movable in response to'motion of a heat control member; a motor to actuate the said heat control member, the said motor being controlled by cooperation of the said movable contacts andthe' said contact carried by the said temperature indicating member; and dashpot means of altering cooperation of the said movable contacts and the said Contact so that resulting control of the rate of heat delivery to' the point under temperature control may be in a predeter- `mined, but changeable,vfunction of the rate of change of temperature at the point under temperature control. l

5. A temperature control systemY having a temperature indicator; an electrical contact carried by the said indicator; a pair of contacts movable in response to motion of a. heat control'member; a motor adapted to act-nate the said heat control member, the said motor being controlledv by cooperation of the said movable contacts and the said contact carried by the said indicating member; and dashpot'` means of altering cooperation of theV said movable contacts and the said contact so that resulting control of tlie said elec.- tric motor, and therefore control of the. rate of heat delivery to the point under temperature control, may be in a predetermined,but changeable, function of rate of change of temperature at the point uilider temperature controlb p 6. A. device of the class described comprising a first contact, and means automatically thermally operable to move the contact in oppositedirectioma pair of contacts fixed to move in unison and' separately engageable with or by the first Contact, a movable element carrying a limit switch, mechanicalconnecmeans for obtaining reversing motions of said movable element, including electrical connections between said limit switch, said first contact, and said pair of contacts, said first and said pair of contacts being slidable with respect to each other. l

7 A device of the class described comprising a first contact, and means automatically thermally operableto move-the contact in oppositiey direction, a pair of contacts fixed to move in unison'and separately engageable with or by the first contact, a movable element carrying a limit switch, mechanicalv connections -for obtaining movements of said pair of contacts, by said movable element, and means for Aobtaining reversing motions of said movable element, including electrical connections between said. limit switch, said first contact, and said pair of contacts, saidy movable element bei g rotatable and said first and said pair of'coiitacts being slidable with respect to each other.

f 8. In a followup control. system, means automatically responsive by movement` to change in physical conditions at point of i control,fa reversing motor, means :for controlling the motor, said controlling means being controlled by said first mentioned means,

means for varying the physical conditions at point of control including a member movable by the motor, and means directly mechanically. controlled by said movable member: and mechanically remote from said first named automatically responsive means for limiting motion of said movable member by breaking an electric circuit for the motor.

9. In a follow up control system, means .automatically responsive by movement to change. in physical conditions atvpoint of control, a reversing motor,.a niot'or control switch controlled by said first named means, circuit ,conductors connecting said first named means andthe motor control switch and also connecting said-motor andmotor control switch, means for varying the physical conditions at point of control including a member movable b the motor, and a limit switch directly mec anically controlled by the motor and mechanically remote from said first named automatically responsive means, for limiting motion ofsaid motor by breaking one of the circuit connections formed by .the above mentioned circuit conductors.l

f 10. In a control system, means automatically responsive by movement to change in `pliysical conditions at point of'control, a reversing motor, a motor control switch, means including interconnecting vcircuit conductors for controlling thecontrol switch by means of said first named automatically .responsive means, means including circuit conductors whereby thereversing motor is controlled by said control switch, means for va ing the physical conditions at the -point orfY control including a memberr movable by the motor, and a limit switch mechanicallyremote from 5 the first named automatically responsive means and connected to the circuit conductors of the control switch control means, said limit switch being directly mechanically controlled byl said motor .and being opratlve to limit 10 movement of the motor by establishing a gap in the circuit of the motor switch control means.

11. In' a control system, means automatically responsive by movement to change in 15 physical conditions at point of control and operating a contact, reversibly movable means for controlling the variation of physicalconditions at point of control, a pair of 'contacts movable in unison and with which zo said first contact is alternatively engageable,

-fmeans by which the' pair of contacts are moved b lsaid condition-varying element, a

. limit switch directly controlled by said condition-varying means and being remote from z5 said first named means, means reversibly electrically operable for correspondingly controlling the condition-varying means, and circuits for controlling said electrically 0perable means including therein all of said con- 80` tacts and said limit switch, whereby motion of a single means directly-controls variation `of the physical conditions, controls the pair of contacts, and controls the limit switch-for directly limiting its own motion.

35 12. Infa control system, means automatically responsive by movement to change in physical conditions at point of control and operating a contact, reversibly movable means for controlling the variation of physi- 4o cal conditions at point of control, a pair of contacts movable 1n unison and wit-h which said first contact is alternatively engageable,

means by which the pair lof contacts are l moved by said condition-varying element,

and means by which said means is adjustable l to vary theratio of the degree of motion be-y tween the pair of contacts and saidcondition'- varyingy means, a limit switch directly controlled by said condition-varying means and I0 being remote from said first named means, means reversibly electricallyv operable for correspondingly controlling the conditionvaryin means, -and circuits for controlling said c elctrically operable means including therein all of said contactsv and said limit switch, whereby motion of a single means directly controls variation of the physical confditions, controls the pair'offcontacts, 'and controls the limit switch for directly limitn in its own motion.

, In witness whereof, I have hereunto set v A my hand this 4th dayof May, 1931. v

.x LEWIS L, CUNNINGHAM. 

